The purpose of the invention is to convert certain hazardous gaseous effluents by chemical reactions into safer solid or gaseous products. Preferably the chemical reagents used are solids and hence reduce the risk of carry-over contamination from the gas conditioning equipment. The solid chemical reagents used are easier and safer to handle than liquid reagents. The solid reagents lend themselves readily to encapsulation in exchangeable cartridges.
The gaseous effluents can be the gases that come from etching of semi-conductor devices or from PECVD (Plasma Enhanced Chemical Vapour Deposition) on to semi-conductor materials: similar gases and vapors are used in several stages of manufacture in the semi-conductor manufacturing process. The effluent gases (and vapors) from reactive ion etching and plasma etching include chlorine, silicon tetrachloride, copper chloride (CuCl), aluminium chlorides (i.e. AlCl.sub.3), silicon tetrafluoride, trifluoromethane (CHF.sub.3), carbonyl fluoride (COF.sub.2), carbonyl chloride (COCl.sub.2), boron trichloride (BCl.sub.3), boron tribromide (BBr.sub.3), hydrogen chloride (HCl), carbon tetrachloride (CCl.sub.4), chlorofluoro carbon gases and others.
Additional gases and vapors that are sometimes found in the effluent of PECVD operations include silane (SiH.sub.4), dichlorosilane (SiCl.sub.2 H.sub.2), tetraethylorthosilicate (Si(OC.sub.2 H.sub.5).sub.4), diborane (B.sub.2 H.sub.6), trimethyl borate (B(OCH.sub.3).sub.3), phosphine (PH.sub.3), trimethylphosphite (P(OCH.sub.3).sub.3), arsine (ASH.sub.3) and others.
The current practice is to allow these gases/vapors to enter an exhaust duct to be transported to a wet scrubber positioned at the exhaust end of the lines. This method is occasionally supplemented by local placement of scrubbers. For etching these may be either:
(a) Of the activated charcoal type to trap the acid gases. This method can trap up to 15% of its charcoal weight of Cl.sub.2. The product is charcoal with the effluent gases trapped but not converted to safer products and some of these effluent gases will be liberated if the charcoal is burnt. PA1 (b) Of the wet type; there are several designs of wet scrubber, most using either a Venturi stage or a packed tower or a combination of both. These designs have been used for larger applications: when placed local to the source of the contamination they present the danger of contamination of the process chamber with their aqueous solutions of caustic type media. The contamination can result from a back streaming type of mechanism or from a massive suckback. PA1 (c) The chemical filter type utilizing a combination of adsorption and chemical adsorption. These are expensive and do not have a good capacity per unit volume. PA1 i) the silicon is not completely coated with the copper to ensure that the copper does not completely passivate the silicon in that both the silicon and the copper play an important role in the reactions in which NF.sub.3 in particular is eliminated from the gas stream as it passes through the exhaust gas conditioning unit; PA1 ii) the silicon and the copper are in intimate physical contact over at least part of the surface areas of the respective particles.
PECVD scrubbers can be as above but often have a Burn box gas conditioning unit introduced locally. These units burn the effluent gases to form their oxides and water vapor. They suffer from blockage problems and there are normally large volumes of oxides to contend with.